Anchor is a heavy weight used to hold a ship or boat in place. A rope or chain is fastened to the anchor and tied to the ship. When the anchor is lowered, it generally catches at the bottom of the water to keep the vessel in place. An anchor may be as simple as a rock tied to the end of a line. The most common kinds of anchors are made of iron or steel.
Anchors come in a wide variety of shapes and sizes. The shape depends in part upon the expected composition of the land at the bottom of the water. For example, when the bottom is mud, a small boat may be held in place by a mushroom anchor, a cast-iron bowl on the end of a rod. But for a rock bottom, the boat would be secured with a grapnel, an anchor with several hooks on its end. The size of the anchor depends mainly on the size of the craft. A huge aircraft carrier may use an anchor weighing more than 60,000 pounds (27,200 kilograms). Anchors are essential for navigation buoys, which must remain in one place at all times and in all kinds of weather. Buoys are held to the bottom by anchors made of concrete.
